The variable nozzle mechanism of the variable geometry turbocharger is for adjusting the flow passage area of exhaust gas inside a turbine casing to change the flow velocity and the pressure of exhaust gas to turbine blades, so as to enhance the effect of supercharging.
As shown in FIG. 19, the variable nozzle mechanism normally includes: a first annular member 012; a second annular member 14 disposed so as to face the first annular member and forming an annular exhaust gas flow passage 24 for guiding exhaust gas from a scroll flow passage 10 formed on the radially outer side of a turbine rotor 2 of the turbocharger to the turbine rotor between the first annular member and the second annular member; and a plurality of nozzle vanes 16 disposed between the first annular member and the second annular member so as to be rotatable and capable of adjusting the flow passage area of the exhaust gas flow passage.
Patent Document 1 discloses a turbocharger comprising a variable nozzle mechanism, wherein an annular partition wall member for partitioning a scroll flow passage and a link chamber is disposed around a nozzle ring (corresponding to the above first annular member). The annular partition wall member is formed of a member separate from a turbine housing, for preventing cracks formed on the partition wall member from reaching the turbine housing.